CN115557558A - Vanadium precipitation wastewater treatment method and system - Google Patents
Vanadium precipitation wastewater treatment method and system Download PDFInfo
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- CN115557558A CN115557558A CN202211184782.XA CN202211184782A CN115557558A CN 115557558 A CN115557558 A CN 115557558A CN 202211184782 A CN202211184782 A CN 202211184782A CN 115557558 A CN115557558 A CN 115557558A
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- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 title claims abstract description 86
- 229910052720 vanadium Inorganic materials 0.000 title claims abstract description 85
- 238000001556 precipitation Methods 0.000 title claims abstract description 69
- 238000004065 wastewater treatment Methods 0.000 title claims abstract description 36
- 239000002351 wastewater Substances 0.000 claims abstract description 103
- 150000003839 salts Chemical class 0.000 claims abstract description 97
- 238000001704 evaporation Methods 0.000 claims abstract description 82
- 230000008020 evaporation Effects 0.000 claims abstract description 80
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 claims abstract description 71
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims abstract description 70
- 229910052921 ammonium sulfate Inorganic materials 0.000 claims abstract description 70
- 235000011130 ammonium sulphate Nutrition 0.000 claims abstract description 70
- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 67
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 67
- 229910001385 heavy metal Inorganic materials 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 33
- 230000008014 freezing Effects 0.000 claims abstract description 32
- 238000007710 freezing Methods 0.000 claims abstract description 32
- 150000002500 ions Chemical class 0.000 claims abstract description 16
- 238000002360 preparation method Methods 0.000 claims abstract description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 95
- 238000002425 crystallisation Methods 0.000 claims description 80
- 230000008025 crystallization Effects 0.000 claims description 80
- 239000012452 mother liquor Substances 0.000 claims description 68
- 238000001728 nano-filtration Methods 0.000 claims description 62
- 239000013078 crystal Substances 0.000 claims description 47
- 230000009615 deamination Effects 0.000 claims description 41
- 238000006481 deamination reaction Methods 0.000 claims description 41
- 238000007670 refining Methods 0.000 claims description 36
- 238000001223 reverse osmosis Methods 0.000 claims description 36
- 238000004519 manufacturing process Methods 0.000 claims description 33
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 30
- 239000011780 sodium chloride Substances 0.000 claims description 14
- 239000011651 chromium Substances 0.000 claims description 11
- 239000007788 liquid Substances 0.000 claims description 11
- 238000010521 absorption reaction Methods 0.000 claims description 10
- 239000002244 precipitate Substances 0.000 claims description 7
- 239000003513 alkali Substances 0.000 claims description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- 239000003638 chemical reducing agent Substances 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 230000001376 precipitating effect Effects 0.000 claims description 4
- 238000010992 reflux Methods 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- VQWFNAGFNGABOH-UHFFFAOYSA-K chromium(iii) hydroxide Chemical compound [OH-].[OH-].[OH-].[Cr+3] VQWFNAGFNGABOH-UHFFFAOYSA-K 0.000 claims description 3
- 238000007865 diluting Methods 0.000 claims description 2
- JUWHRJSDVJDFJG-UHFFFAOYSA-J vanadium(4+);tetrahydroxide Chemical compound [OH-].[OH-].[OH-].[OH-].[V+4] JUWHRJSDVJDFJG-UHFFFAOYSA-J 0.000 claims 1
- 230000008901 benefit Effects 0.000 abstract description 4
- 239000011734 sodium Substances 0.000 description 10
- 239000000047 product Substances 0.000 description 9
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 8
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 6
- 230000002378 acidificating effect Effects 0.000 description 6
- 238000005406 washing Methods 0.000 description 6
- 239000012528 membrane Substances 0.000 description 5
- -1 V 5+ Chemical class 0.000 description 4
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 description 4
- 238000005057 refrigeration Methods 0.000 description 4
- 238000000108 ultra-filtration Methods 0.000 description 4
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 3
- 229910021529 ammonia Inorganic materials 0.000 description 3
- XKMRRTOUMJRJIA-UHFFFAOYSA-N ammonia nh3 Chemical compound N.N XKMRRTOUMJRJIA-UHFFFAOYSA-N 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- 238000000605 extraction Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000001953 recrystallisation Methods 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 239000013049 sediment Substances 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 229910052708 sodium Inorganic materials 0.000 description 3
- 235000015424 sodium Nutrition 0.000 description 3
- HRZFUMHJMZEROT-UHFFFAOYSA-L sodium disulfite Chemical compound [Na+].[Na+].[O-]S(=O)S([O-])(=O)=O HRZFUMHJMZEROT-UHFFFAOYSA-L 0.000 description 3
- 229940001584 sodium metabisulfite Drugs 0.000 description 3
- 235000010262 sodium metabisulphite Nutrition 0.000 description 3
- 231100000331 toxic Toxicity 0.000 description 3
- 230000002588 toxic effect Effects 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- RAHZWNYVWXNFOC-UHFFFAOYSA-N Sulphur dioxide Chemical compound O=S=O RAHZWNYVWXNFOC-UHFFFAOYSA-N 0.000 description 2
- QKDGGEBMABOMMW-UHFFFAOYSA-I [OH-].[OH-].[OH-].[OH-].[OH-].[V+5] Chemical compound [OH-].[OH-].[OH-].[OH-].[OH-].[V+5] QKDGGEBMABOMMW-UHFFFAOYSA-I 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 2
- 230000006378 damage Effects 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 238000001640 fractional crystallisation Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 239000010802 sludge Substances 0.000 description 2
- 159000000000 sodium salts Chemical class 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 201000004624 Dermatitis Diseases 0.000 description 1
- 206010058467 Lung neoplasm malignant Diseases 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 208000026935 allergic disease Diseases 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 150000001844 chromium Chemical class 0.000 description 1
- BFGKITSFLPAWGI-UHFFFAOYSA-N chromium(3+) Chemical compound [Cr+3] BFGKITSFLPAWGI-UHFFFAOYSA-N 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 230000001079 digestive effect Effects 0.000 description 1
- 210000002249 digestive system Anatomy 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 238000012851 eutrophication Methods 0.000 description 1
- 238000011066 ex-situ storage Methods 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 210000002216 heart Anatomy 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 210000003734 kidney Anatomy 0.000 description 1
- 238000002386 leaching Methods 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 201000005202 lung cancer Diseases 0.000 description 1
- 208000020816 lung neoplasm Diseases 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 210000000653 nervous system Anatomy 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910017464 nitrogen compound Inorganic materials 0.000 description 1
- 150000002830 nitrogen compounds Chemical class 0.000 description 1
- 235000015097 nutrients Nutrition 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 230000000241 respiratory effect Effects 0.000 description 1
- 210000002345 respiratory system Anatomy 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000009287 sand filtration Methods 0.000 description 1
- 239000010865 sewage Substances 0.000 description 1
- 210000003491 skin Anatomy 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 235000010269 sulphur dioxide Nutrition 0.000 description 1
- PSDQQCXQSWHCRN-UHFFFAOYSA-N vanadium(4+) Chemical compound [V+4] PSDQQCXQSWHCRN-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/24—Sulfates of ammonium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
- C01D5/16—Purification
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/441—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by reverse osmosis
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
- C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/101—Sulfur compounds
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2101/00—Nature of the contaminant
- C02F2101/10—Inorganic compounds
- C02F2101/16—Nitrogen compounds, e.g. ammonia
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
- C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
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Abstract
The invention provides a vanadium precipitation wastewater treatment method and a vanadium precipitation wastewater treatment system. The vanadium precipitation wastewater treatment method comprises a weight removal step and a salt preparation step which are sequentially carried out, wherein sodium sulfate and ammonium sulfate are respectively obtained in the salt preparation step, and the salt preparation step comprises a first evaporation step, a freezing step and a second evaporation step. Sodium sulfate and ammonium sulfate were obtained in two evaporation steps, respectively. By the wastewater treatment method, heavy metal ions in the wastewater can be effectively removed, salts in the wastewater can be respectively extracted and reused, and economic benefits can be greatly improved. The invention also provides a vanadium precipitation wastewater treatment system for implementing the treatment method.
Description
Technical Field
The invention relates to the field of sewage treatment, in particular to a vanadium precipitation wastewater treatment method and a vanadium precipitation wastewater treatment system.
Background
The waste water generated in the process of preparing vanadium pentoxide is called vanadium precipitation waste water, and the waste water contains certain V 5+ 、Cr 6 + Besides heavy metal ions, the catalyst also contains a large amount of NH 4 + 、Na + 、SO 4 2- 、Cl - And the like. As the technology level of the past process for treating vanadium precipitation wastewater is laggard, a large amount of vanadium-containing waste salt which is difficult to treat is generated in the wastewater treatment process of part of enterprises, and the main component of the vanadium-containing waste salt is Na 2 SO 4 Also contains a certain amount of V 5+ 、Cr 6+ 、NH 4 + 、Cl - And the like.
The vanadium precipitation wastewater has the following characteristics:
1. the vanadium precipitation wastewater is acidic. Because the production process of vanadium pentoxide adopts acid to leach, and the process requires that the vanadium precipitation process is carried out under certain acidic condition, the wastewater is acidic.
2. The vanadium precipitation wastewater contains a large amount of toxic heavy metal ions, particularly V 5+ 、Cr 6+ The content is higher and is far higher than the highest allowable discharge concentration of the first pollutant in the integrated wastewater discharge standard. Because the vanadium precipitation wastewater mainly comes from the vanadium precipitation process, V in the raw materials in the leaching, precipitation and washing processes 5+ 、Cr 6+ The wastewater is formed as the water enters the liquid phase, so that the wastewater contains a large amount of V 5+ 、Cr 6+ 。
3. SO in wastewater 4 2- Has a higher concentration and a higher salt content. The common vanadium extraction method is sodium roasting. Due to the sodium roasting method in the preparation of raw materialsA certain amount of Na needs to be added in the process 2 CO 3 And the acid used in the sodium salt roasting process is sulfuric acid, so that waste water Na is generated + 、SO 4 2- The concentration is higher. The sodium salt roasting adopts ammonium salt to precipitate vanadium and NH in the vanadium precipitation process 4 + All the ammonia nitrogen is transferred into the wastewater, so that the ammonia nitrogen concentration in the vanadium precipitation wastewater is higher.
In the human body, cr 6+ Insoluble chromium salt can be formed, which is an important factor for causing lung cancer; v 5+ Can cause harm to the respiratory, digestive and nervous systems of human bodies, damage to the skin, heart and kidney, and cause skin inflammation and allergic diseases. In addition, the wastewater containing high concentration ammonia nitrogen can cause certain hazards, such as: consumes dissolved oxygen in water, accelerates the release of nutrient substances in the water body, influences water sources, increases the toxic action of nitrogen compounds on human bodies and organisms, causes water body eutrophication and the like. According to estimation, the vanadium extraction process by the sodium roasting method is adopted to extract V at the production rate of 1 ton 2 O 5 With generation of about 60m 3 The vanadium precipitation wastewater. The production of a large amount of vanadium precipitation wastewater and waste salt causes serious pollution to the environment and seriously influences the sustainable development of the vanadium industry.
The treatment of the vanadium precipitation wastewater in the prior art usually focuses on removing toxic heavy metal ions in the wastewater. For example, CN102795721A discloses a method for treating acidic wastewater containing precipitated vanadium, which can avoid heavy metal pollution by reducing high-valence vanadium (V) and chromium (VI) into low-valence vanadium (IV) and chromium (III), then converting them into hydroxide precipitates to remove them, and then discharging the wastewater, but other compounds remaining in the wastewater are not treated, and thus resource reutilization cannot be fully realized.
Disclosure of Invention
In view of the technical problems in the prior art, the invention aims to respectively extract the salt in the vanadium precipitation wastewater after heavy metal ions are removed so as to fully realize resource recycling.
The invention provides a vanadium precipitation wastewater treatment method, which comprises a weight removal step and a salt preparation step which are sequentially carried out, wherein sodium sulfate and ammonium sulfate are respectively obtained in the salt preparation step, and the salt preparation step comprises the following steps:
a first evaporation step: carrying out first evaporation on the weight removal wastewater obtained in the weight removal step to obtain primary evaporative crystals and primary evaporative crystal mother liquor, wherein the primary evaporative crystals contain sodium sulfate;
a freezing step: freezing the primary evaporation crystallization mother liquor to obtain double salt and frozen mother liquor, wherein the double salt comprises sodium sulfate and ammonium sulfate, and refluxing the double salt into the wastewater after the heavy metals are removed;
and a second evaporation step: and carrying out secondary evaporation on the frozen mother liquor to obtain secondary evaporative crystals and a secondary evaporative crystal mother liquor, wherein the secondary evaporative crystals contain ammonium sulfate.
The vanadium precipitation wastewater after most suspended matters and heavy metal ions are removed mainly contains two inorganic salts of sodium sulfate and ammonium sulfate. After the heavy metal ions in the wastewater are removed by adopting the vanadium precipitation wastewater treatment method, other compounds available in the wastewater, such as sodium sulfate, ammonium sulfate and the like, can be extracted through a salt preparation step. The treatment method can completely separate the sodium sulfate and the ammonium sulfate, so that the two compounds can be utilized according to respective purposes, and the separation method is simple and efficient, has low operation cost and can greatly improve the economic benefit.
Preferably, the salt manufacturing step further comprises a refining step: and refining the primary evaporative crystals and the secondary evaporative crystals respectively to obtain refined sodium sulfate and refined ammonium sulfate.
The main process adopted in the refining step is recrystallization or salt washing. If recrystallization is adopted for refining, primary evaporative crystallization and secondary evaporative crystallization containing certain impurities are respectively dissolved and then recrystallized, and sodium sulfate and ammonium sulfate in the primary evaporative crystallization and the secondary evaporative crystallization are respectively purified to obtain refined sodium sulfate and refined ammonium sulfate. Specifically, the temperature for recrystallizing the primary evaporative crystals is 60-120 ℃, and the temperature for recrystallizing the secondary evaporative crystals is 60-120 ℃.
Of course, in other possible embodiments of the present invention, the refining step may also be performed using a salt washing process. When the salt washing process is adopted for refining treatment, the salt washing water amount is as follows: the mass ratio of the crystal salt is (1-2): 1, continuously returning the washed salt-washing wastewater to respective evaporative crystallization systems, and allowing the washed salt to enter a centrifugal drying system to discharge product salt.
Preferably, the salt making step further comprises:
and (4) nanofiltration: diluting the secondary evaporation crystallization mother liquor by 4-8 times, and then performing nanofiltration for more than one time to obtain nanofiltration concentrated water and nanofiltration produced water, so that the nanofiltration concentrated water is refluxed and is merged into the heavy wastewater or the frozen mother liquor;
and (3) deamination: and (3) deaminating the nanofiltration water product to obtain deamination absorption liquid and deamination water product, wherein the deamination water product enters a reverse osmosis system, and the deamination absorption liquid contains ammonium sulfate.
The secondary evaporation crystallization mother liquor can be diluted by water meeting the production and reuse standard at any section in the system, such as reverse osmosis produced water or evaporation condensate.
Nanofiltration is a commonly used process for separating monovalent and divalent ions, such as sulfate and chloride, from a solution. In the invention, through carrying out nanofiltration more than once, naCl and (NH) are led to 4 ) 2 SO 4 、Na 2 SO 4 The water is enriched at the water production side and the concentrated water side respectively, nanofiltration concentrated water mainly containing ammonium sulfate and sodium sulfate reflows to a freezing system to further extract the sodium sulfate, and nanofiltration water production mainly containing sodium chloride is subjected to a deamination step to thoroughly remove residual ammonium ions in the water after nanofiltration.
During the practical production process, the nanofiltration concentrated water is refluxed and merged into the primary evaporation crystallization mother liquor or the freezing mother liquor according to the water quality of the nanofiltration concentrated water. Specifically, according to the concentration of sodium sulfate in the nanofiltration concentrated water, if the concentration of sodium sulfate in the nanofiltration concentrated water is less than or equal to 2%, namely the total salt content in the wastewater is calculated, and the sodium sulfate accounts for less than 2%, the nanofiltration concentrated water is merged into the freezing mother liquor for secondary evaporation to prepare ammonium sulfate; if the concentration of sodium sulfate in the nanofiltration concentrated water is more than 2 percent, the nanofiltration concentrated water is merged into the primary evaporative crystallization mother liquor to be frozen to obtain the double salt. Sodium sulfate and ammonium sulfate in the wastewater are sufficiently obtained through the treatment.
Preferably, the nitrogen content in the deamination water is below 25 mg/L.
Preferably, the salt making step further comprises:
reverse osmosis: performing reverse osmosis on the deamination produced water to obtain reverse osmosis concentrated water and reverse osmosis produced water, wherein the reverse osmosis produced water meets the production and reuse requirements;
and (3) a third evaporation step: and (3) carrying out third evaporation on the reverse osmosis concentrated water to obtain third evaporation crystals, and refining the third evaporation crystals to obtain refined sodium chloride. The refined sodium chloride meets the GB/T5462-2015 industrial salt standard, and specifically at least meets the secondary standard of industrial wet salt in the GB/T5462-2015 industrial salt.
The sodium chloride product can be obtained by reverse osmosis and evaporative crystallization of the deamination water. By adopting the vanadium precipitation wastewater treatment method, sodium sulfate, ammonium sulfate and sodium chloride salt in the wastewater can be obtained, and the full utilization of resources is realized.
Preferably, the concentration of ammonium sulfate in the mother liquor of the primary evaporation crystallization is below 50%, and/or the content of sodium sulfate in the double salt is above 70%.
As the first evaporation step is carried out, ammonium sulfate in the waste water is controlled not to be separated out as much as possible in the concentration process so as to obtain a primary evaporation crystal mainly containing sodium sulfate. Preferably, the ammonium sulfate content in the mother liquor of the primary evaporative crystallization is below 50%, and the concentration degree can avoid obtaining ammonium sulfate crystals in the step. More preferably, the concentration of ammonium sulfate in the mother liquor of the primary evaporation crystallization is 40-50%, so that the sodium sulfate can be precipitated as much as possible in the primary evaporation process, and the ammonium sulfate can be remained in the mother liquor. The main effect of the freezing step is to separate sodium sulfate and ammonium sulfate in the wastewater as much as possible, and it is desirable that sodium sulfate is precipitated as much as possible, and ammonium sulfate is retained in the mother liquor as much as possible, and therefore, the double salt precipitated in the freezing step should mainly contain sodium sulfate, and the content of sodium sulfate is 70% or more, preferably 80% or more, and more preferably 90% or more. The content of sodium sulfate in the obtained double salt is slightly different according to different mother liquor systems. Further separation of sodium sulfate and ammonium sulfate in the mother liquor is realized through a freezing step, so that double salts mainly containing sodium sulfate return to the wastewater for removing the heavy metals to participate in first evaporation to prepare sodium sulfate, and the frozen mother liquor mainly containing ammonium sulfate enters the next step to be evaporated for the second time to prepare ammonium sulfate.
Preferably, the vanadium precipitation wastewater treatment method also meets more than one of the following processes:
when the heavy wastewater is evaporated for the first time, the evaporation temperature is 80-120 ℃;
when the primary evaporative crystallization mother liquor is frozen, the freezing temperature is-5 ℃;
when the freezing mother liquor is evaporated for the second time, the evaporation temperature is 60-120 ℃.
The reaction temperature of the evaporation process can be adjusted according to the specific situation of evaporation crystallization. For example, if the presence of ammonium sulfate is detected in the first evaporative crystallization, the temperature of evaporative concentration may be appropriately raised to dissolve ammonium sulfate. Preferably, the evaporation temperature of the first evaporation of the heavy wastewater is 80-120 ℃, more preferably 100-120 ℃, and the higher the temperature, the more sodium sulfate is precipitated.
The vanadium precipitation wastewater contains Cr 6+ And V 5+ Preferably, the step of removing the heavy metal comprises the steps of adding a reducing agent into the vanadium precipitation wastewater, fully stirring, adding alkali to adjust the pH value to 8-10 to obtain heavy metal precipitate and heavy metal removal wastewater, wherein the heavy metal precipitate contains chromium hydroxide (III) and vanadium hydroxide (IV), and adjusting the pH value of the heavy metal removal wastewater to 4-6 to carry out a salt preparation step.
The method for treating the vanadium precipitation wastewater comprises the following steps of dissolving the mixed salt generated in the vanadium extraction process by using the vanadium precipitation wastewater, dissolving the mixed salt into the vanadium precipitation wastewater to be treated, and carrying out combined treatment on the mixed salt and the vanadium precipitation wastewater.
Specifically, after dissolving the miscellaneous salt in the vanadium precipitation wastewater, reducing high-valence vanadium and chromium in the wastewater under an acidic condition, wherein the used reducing agent can be common reducing agents such as sodium metabisulfite, ferrous sulfate, sulfur dioxide and the like. The alkali added in the process of precipitating the heavy metal ions can be sodium hydroxide or lime and other alkali substances commonly used in the industry. Removing heavy metal precipitate to obtain heavy metal-removed wastewater, adjusting the pH of the heavy metal-removed wastewater to 4-6, and then performing a salt making step.
Preferably, the total chromium in the heavy wastewater is less than or equal to 0.05mg/L and the total vanadium is less than or equal to 0.05mg/L. Through the heavy metal removing step, heavy metal ions in the wastewater are basically removed, and the quality of the finished salt is not influenced.
By adopting the treatment method to treat the vanadium precipitation wastewater system, more than 97wt% of salt in the wastewater system can be recovered, the salt impurity rate is reduced to less than 3wt%, and the full utilization of resources can be realized.
Preferably, the refined sodium sulfate at least meets the indexes of GB/T6009-2014 in the class III of anhydrous sodium sulfate; and/or, the content of ammonium sulfate in the refined ammonium sulfate is more than 95%, preferably more than 98%.
The sodium sulfate, the ammonium sulfate and the sodium chloride obtained by the vanadium precipitation wastewater treatment method can be directly utilized, and resource circulation can be fully realized.
In a second aspect of the invention, a vanadium precipitation wastewater treatment system is disclosed, which is used for implementing the vanadium precipitation wastewater treatment method. The treatment system comprises a weight removal system and a salt production system; the heavy metal ion that removes in the heavy system of removing vanadium waste water obtains removing heavy waste water, and the salt system is used for removing heavy waste water and handles, obtains sodium sulfate and ammonium sulfate.
Preferably, the salt production system comprises a primary evaporative crystallization system, a refrigeration system and a secondary evaporative crystallization system;
the primary evaporative crystallization system is used for carrying out primary evaporation on the heavy wastewater to obtain primary evaporative crystallization and primary evaporative crystallization mother liquor;
the freezing system is used for freezing the primary evaporative crystallization mother liquor to obtain double salt and freezing mother liquor;
and the secondary evaporation crystallization system is used for carrying out secondary evaporation on the frozen mother liquor to obtain secondary evaporation crystals and secondary evaporation crystal mother liquor.
Preferably, the treatment system further comprises a first refining system and a second refining system, the feed inlet of the first refining system is connected with the other discharge outlet of the primary evaporative crystallization system, the feed inlet of the second refining system is connected with the other discharge outlet of the secondary evaporative crystallization system, and the first refining system and the second refining system are respectively used for refining the primary evaporative crystallization and the secondary evaporative crystallization.
Preferably, the treatment system further comprises a nanofiltration system and a deammoniation system;
the nanofiltration system is used for carrying out nanofiltration on the secondary evaporative crystallization mother liquor for more than one time to obtain nanofiltration concentrated water and nanofiltration produced water;
the discharge port of the nanofiltration system can be connected with a refrigeration system or a secondary evaporation crystallization system and is judged according to the content of sodium sulfate in nanofiltration concentrated water. Generally, in the earlier stage of wastewater treatment, the content of ammonium sulfate in nanofiltration concentrated water is high, and the nanofiltration concentrated water enters a secondary evaporation crystallization system. With the progress of the wastewater treatment process, sodium sulfate remained in the secondary evaporation crystallization mother liquor can be enriched, and after the sodium sulfate enters the nanofiltration system, the content of sodium sulfate in the nanofiltration concentrated water is increased, and at the moment, the nanofiltration concentrated water enters the refrigeration system. The deamination system is used for carrying out deamination on the nanofiltration water production to obtain deamination absorption liquid and deamination water production, wherein the deamination absorption liquid contains ammonium sulfate.
Preferably, the deamination system comprises a deamination membrane, ammonia gas is obtained from nanofiltration water production through the deamination membrane, and a pure ammonium sulfate solution is obtained after the ammonia gas is absorbed by concentrated sulfuric acid.
Preferably, the treatment system further comprises a reverse osmosis system, a tertiary evaporative crystallization system and a third refining system;
a feed inlet of the reverse osmosis system is connected with a discharge outlet of the deamination system, and the reverse osmosis system is used for performing reverse osmosis on deamination produced water to obtain reverse osmosis concentrated water and reverse osmosis produced water;
the feed inlet of the tertiary evaporative crystallization system is connected with the discharge outlet of the reverse osmosis system, and the tertiary evaporative crystallization system is used for carrying out tertiary evaporation on reverse osmosis concentrated water to obtain tertiary evaporative crystals;
and a feed inlet of the third refining system is connected with a discharge outlet of the third evaporative crystallization system, and the third refining system is used for refining the third evaporative crystallization to obtain refined sodium chloride.
Drawings
FIG. 1 shows a flow chart of a vanadium precipitation wastewater treatment method according to the present invention;
FIG. 2 shows a flow chart of a vanadium precipitation wastewater treatment system in one embodiment of the invention.
Reference numerals:
1-a salt dissolving system, 2-a crushing system, 3-a pretreatment system, 4-a dosing system, 5-a sedimentation tank, 6-a sludge tank, 7-a plate and frame filter press, 8-a water production tank, 9-sand filtration, an ultrafiltration tank, 10-a primary evaporative crystallization system, 11-a refrigeration system, 12-a secondary evaporative crystallization system, 13-a nanofiltration system, 14-a second refining system, 15-a first refining system, 16-a nanofiltration system, 17-a deamination system, 18-a reverse osmosis system, 19-a tertiary evaporative crystallization system and 20-a third refining system.
Detailed Description
The following description is given by way of example of the present invention and other advantages and features of the present invention will become apparent to those skilled in the art from the following detailed description. While the invention will be described in conjunction with the preferred embodiments, it is not intended that features of the invention be limited to these embodiments. On the contrary, the invention is described in connection with the embodiments for the purpose of covering alternatives or modifications that may be extended based on the claims of the present invention. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be practiced without these particulars. Moreover, some of the specific details have been left out of the description in order to avoid obscuring or obscuring the focus of the present invention. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.
It should be noted that in this specification, like reference numerals and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.
The terms "first," "second," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.
In the description of the present embodiment, it should be further noted that, unless explicitly stated or limited otherwise, the terms "disposed," "connected," and "connected" are to be interpreted broadly, e.g., as a fixed connection, a detachable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. Specific meanings of the above terms in the present embodiment can be understood as specific cases by those of ordinary skill in the art.
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Examples
FIG. 1 is a flow chart of the vanadium precipitation wastewater treatment method of the invention. The heavy vanadium precipitation wastewater after the weight removal mainly contains two inorganic salts of sodium sulfate and ammonium sulfate. Through removing heavy step and salt manufacturing step to heavy vanadium waste water in proper order, can obtain sodium sulfate and ammonium sulfate respectively in the salt manufacturing step, wherein, the salt manufacturing step includes:
a first evaporation step: performing primary evaporation on the heavy removal wastewater obtained in the heavy removal step to obtain primary evaporative crystals and primary evaporative crystal mother liquor, wherein the primary evaporative crystals contain sodium sulfate;
a freezing step: freezing the primary evaporation crystallization mother liquor to obtain double salt and frozen mother liquor, wherein the double salt comprises sodium sulfate and ammonium sulfate, and refluxing the double salt into the wastewater after the heavy metals are removed;
and a second evaporation step: and carrying out secondary evaporation on the frozen mother liquor to obtain secondary evaporative crystals and a secondary evaporative crystal mother liquor, wherein the secondary evaporative crystals contain ammonium sulfate.
Specifically, na is used 2 SO 4 And (NH) 4 ) 2 SO 4 The co-saturation point of (A) is first evaporated in a first evaporation step to extract part of Na 2 SO 4 Freezing for crystallizing to extract compound salt, and evaporating for concentration for the second time to obtain (NH) 4 ) 2 SO 4 . The double salt separated in the freezing crystallization process is returned to the raw water which is not evaporated and concentrated to dissolve and participate in the next fractional crystallization, so that more sodium sulfate is produced and ammonium radicals are further concentrated. In the freezing step, the sodium sulfate and the ammonium sulfate are separated as much as possible by mainly utilizing the content and solubility difference of the sodium sulfate and the ammonium sulfate in the solution, so that the sodium sulfate with low solubility in the primary evaporation crystallization mother liquor is separated out as much as possible, and the ammonium sulfate with high solubility in the primary evaporation crystallization mother liquor is remained in the mother liquor as much as possible, thereby ensuring the purity of the ammonium sulfate crystal salt obtained subsequently. The content of sodium sulfate in the primary evaporative crystallization is more than 92 percent, and the specific content is slightly different according to different wastewater systems.
Na in the wastewater can be fully and effectively recovered through a fractional crystallization process 2 SO 4 And (NH) 4 ) 2 SO 4 The method can effectively and thoroughly separate the sodium sulfate and the ammonium sulfate in the wastewater to respectively obtain the sodium sulfate and the ammonium sulfate.
FIG. 2 is a flow chart of a vanadium precipitation wastewater treatment system in another embodiment of the present invention. Referring to FIG. 2, 130g of miscellaneous salt is crushed by a crushing system 2 and then fully dissolved and mixed by a salt dissolving system 1 and 1L of vanadium precipitation wastewater. Wherein the water quality of the vanadium precipitation wastewater before dissolving the miscellaneous salts is shown in Table 1, and the water quality of the vanadium precipitation wastewater after dissolving the miscellaneous salts is shown in Table 2.
TABLE 1
TABLE 2
Mixing and stirring in a salt dissolving system 1 to fully dissolve miscellaneous salt in the vanadium precipitation wastewater. As shown in table 2, the precipitated vanadium wastewater after the dissolution of the miscellaneous salts was acidic, and pH =2. The dosing system 4 is utilized to feed the pretreatment system 3 with chromium (VI): sodium metabisulfite =1:5 (mass ratio) of sodium metabisulfite. Liquid alkali, such as sodium hydroxide solution, is added into the pretreatment system 3, and the pH of the vanadium precipitation wastewater after dissolving the miscellaneous salts is adjusted to 8.5. And (3) fully stirring the mixture, and then entering a sedimentation tank 5 to obtain heavy metal sediment and heavy metal removal wastewater, wherein the heavy metal sediment contains chromium hydroxide (III) and vanadium hydroxide (IV), and the heavy metal sediment is subjected to ex-situ treatment after passing through a sludge tank 6 and a plate-and-frame filter press 7. The heavy wastewater enters a water producing tank 8 and a sand filtering and ultrafiltration tank 9 in sequence, most suspended matters remained in the boiling water are removed after sand filtering and ultrafiltration, and the salt making step is carried out after the pH of the sand ultrafiltration effluent is adjusted to 4.5 by adding sulfuric acid. After heavy metal ions are removed, the content of chromium in the heavy metal removal wastewater is less than 0.05mg/L, and the content of vanadium is less than 0.05mg/L. The heavy metal ions in the vanadium precipitation wastewater can be effectively removed by the heavy metal removing step adopted by the embodiment.
The wastewater after the weight removal is evaporated for the first time in the primary evaporation crystallization system 10, wherein the evaporation temperature is 100 ℃, the mass fraction of sodium sulfate in the wastewater after the weight removal is 20%, and the mass fraction of ammonium sulfate is 3%. When the heavy wastewater is concentrated by 1.9 times, salt precipitation is started, the wastewater is continuously evaporated to obtain primary evaporative crystals and primary evaporative crystal mother liquor, and the content of sodium sulfate in the precipitated primary evaporative crystals is about 95%. Ammonium sulfate begins to precipitate after 16 times of concentration, the concentration of the ammonium sulfate in the mother liquor is close to 50%, the content of ammonia nitrogen-N is about 10 ten thousand ppm, the evaporation emphasis is controlled to be that the content of ammonia nitrogen-N is less than or equal to 10 ten thousand ppm, namely, the first evaporation degree is controlled to stop when the ammonium sulfate begins to precipitate, sodium sulfate with high precipitation quality is ensured, and the precipitated sodium sulfate crystals account for more than 90% of the total content of the sodium sulfate in the wastewater.
The primary evaporation crystallization mother liquor enters a freezing system 11, the temperature of the freezing system is 0 ℃, the concentration of sodium sulfate in the primary evaporation crystallization mother liquor is about 10%, the concentration of sodium chloride is 4.27%, the concentration of ammonium sulfate is 39%, double salt and freezing mother liquor are obtained in the freezing system 11, the double salt mainly comprises sodium sulfate and ammonium sulfate, and the content of the sodium sulfate is more than 70%. Thereafter, the double salt is refluxed to the primary evaporative crystallization system 10 to produce more sodium sulfate and further concentrate ammonium radicals.
And (3) carrying out secondary evaporation on the frozen mother liquor in a secondary evaporation crystallization system 12, wherein the evaporation temperature is 80 ℃, so as to obtain secondary evaporation crystallization and secondary evaporation crystallization mother liquor, the content of ammonium sulfate in the secondary evaporation crystallization is about 95%, and the precipitated ammonium sulfate accounts for more than 50% of the total content of ammonium sulfate in the wastewater.
The primary evaporative crystals and the secondary evaporative crystals obtained through the steps contain a small amount of other impurities, and therefore the primary evaporative crystals and the secondary evaporative crystals enter the first refining system 15 and the second refining system 14 respectively for recrystallization, and refined sodium sulfate and refined ammonium sulfate are obtained after refining, wherein the refined sodium sulfate can meet the indexes of GB/T6009-2014 industrial anhydrous sodium sulfate class II, and the content of ammonium sulfate in the refined ammonium sulfate is more than 98%.
And (3) carrying out nanofiltration and deamination on the secondary evaporative crystallization mother liquor obtained through the steps. The secondary evaporative crystallization mother liquor is diluted by 6 times by reverse osmosis produced water and then sequentially passes through two nanofiltration systems, namely a nanofiltration system I13 and a nanofiltration system II 14, wherein the two sections have different nanofiltration pressures and are used for further concentrating the salt in the mother liquor. The water quality of the mother liquor of the secondary evaporative crystallization is shown in Table 3, and the water quality of the mother liquor of the diluted secondary evaporative crystallization is shown in Table 4.
TABLE 3
TABLE 4
Nanofiltration can separate monovalent ions and divalent ions in the mother liquor, so that sodium chloride and ammonium sulfate are enriched on the water production side and the concentrated water of the nanofiltration membrane respectively, namely the nanofiltration water mainly contains sodium chloride, and the nanofiltration concentrated water mainly contains ammonium sulfate and a small amount of sodium sulfate.
At this time, the nanofiltration concentrated water is introduced into the secondary evaporative crystallization system 12 as shown in table 5 according to the quality of the nanofiltration concentrated water in the nanofiltration system 13.
TABLE 5
The water quality of the nanofiltration produced water is shown in table 6.
TABLE 6
As can be seen from Table 6, the nanofiltration product water still contains a certain amount of ammonium radicals, and therefore, the nanofiltration product water enters a deamination system 17 to be deaminated, so as to obtain deamination absorption liquid and deamination product water. The deamination system that adopts in this embodiment includes the deamination membrane, and the nanofiltration product water obtains the ammonia through the deamination membrane, after concentrated sulfuric acid absorbs, obtains pure ammonium sulfate solution. Because the deamination absorption liquid is pure ammonium sulfate solution, the deamination absorption liquid is directly dried by a fluidized bed to obtain pure ammonium sulfate salt. The water quality of the deamination water is shown in Table 7, and the component is mainly sodium chloride.
TABLE 7
The deamination water is condensed by 3 times in a reverse osmosis system 18 to obtain reverse osmosis concentrated water and reverse osmosis water. The reverse osmosis water can reach the production and reuse standard.
And (3) the reverse osmosis concentrated water enters a tertiary evaporation crystallization system 19 for tertiary evaporation, the evaporation temperature is 120 ℃, tertiary evaporation crystallization is obtained, and the tertiary evaporation crystallization is refined in a third refining system 20 to obtain refined sodium chloride.
The remaining mother liquor enters a miscellaneous salt system (not shown) to remove miscellaneous salts. Through the vanadium precipitation wastewater treatment process, three kinds of crystal salt are obtained through three times of evaporative crystallization, and salt separation recovery can be realized. Through calculation, the final integral miscellaneous salt rate is 1.34 percent and is below 3 weight percent, which shows that the resource reutilization of the vanadium precipitation wastewater can be realized to the maximum extent by adopting the vanadium precipitation wastewater treatment method and the vanadium precipitation wastewater treatment system.
While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing is a more particular description of the invention than is possible with reference to the specific embodiments, and the specific embodiments of the invention are not to be considered as limited to those descriptions. Various changes in form and detail, including simple deductions or substitutions, may be made by those skilled in the art without departing from the spirit and scope of the invention.
Claims (13)
1. The vanadium precipitation wastewater treatment method is characterized by comprising a weight removal step and a salt preparation step which are sequentially carried out, wherein sodium sulfate and ammonium sulfate are respectively obtained in the salt preparation step, and the salt preparation step comprises the following steps:
a first evaporation step: carrying out first evaporation on the weight removal wastewater obtained in the weight removal step to obtain primary evaporative crystals and primary evaporative crystal mother liquor, wherein the primary evaporative crystals contain sodium sulfate;
a freezing step: freezing the primary evaporative crystallization mother liquor to obtain double salt and frozen mother liquor, wherein the double salt comprises sodium sulfate and ammonium sulfate, and refluxing the double salt into the wastewater after the weight is removed;
a second evaporation step: and carrying out second evaporation on the frozen mother liquor to obtain second evaporative crystals and a second evaporative crystal mother liquor, wherein the second evaporative crystals contain ammonium sulfate.
2. The method for treating vanadium precipitation wastewater according to claim 1, wherein the salt production step further comprises a refining step: and refining the primary evaporative crystal and the secondary evaporative crystal respectively to obtain refined sodium sulfate and refined ammonium sulfate.
3. The vanadium precipitation wastewater treatment method according to claim 2, wherein the salt production step further comprises:
and (4) nanofiltration: diluting the secondary evaporative crystallization mother liquor by 4-8 times, and then performing nanofiltration for more than one time to obtain nanofiltration concentrated water and nanofiltration produced water, and refluxing the nanofiltration concentrated water to be merged into the primary evaporative crystallization mother liquor or the freezing mother liquor;
and (3) deamination step: and (3) deaminating the nanofiltration water production to obtain deamination absorption liquid and deamination water production, wherein the deamination absorption liquid contains ammonium sulfate.
4. The vanadium precipitation wastewater treatment method according to claim 3, wherein the salt production step further comprises:
reverse osmosis: performing reverse osmosis on the deamination produced water to obtain reverse osmosis concentrated water and reverse osmosis produced water, wherein the reverse osmosis produced water meets the production and reuse standard;
and (3) a third evaporation step: and (3) evaporating the reverse osmosis concentrated water for the third time to obtain evaporation crystals for the third time, and refining the evaporation crystals for the third time to obtain refined sodium chloride, wherein the refined sodium chloride meets the GB/T5462-2015 industrial salt standard.
5. The method for treating vanadium precipitation wastewater according to claim 1, wherein the concentration of ammonium sulfate in the primary evaporative crystallization mother liquor is below 50%, and/or the content of sodium sulfate in the double salt is above 70%.
6. The vanadium precipitation wastewater treatment method according to any one of claims 1 to 5, wherein one or more of the following processes are satisfied:
when the heavy wastewater is evaporated for the first time, the evaporation temperature is 80-120 ℃;
when the primary evaporative crystallization mother liquor is frozen, the freezing temperature is-5 ℃;
and when the freezing mother liquor is evaporated for the second time, the evaporation temperature is 60-120 ℃.
7. The vanadium precipitation wastewater treatment method according to claim 1, wherein the vanadium precipitation wastewater contains Cr 6+ And V 5+ Adding a reducing agent into the vanadium precipitation wastewater, fully stirring, adding alkali to adjust the pH value to 8-10 to obtain heavy metal precipitate and heavy metal removal wastewater, wherein the heavy metal precipitate contains chromium (III) hydroxide and vanadium (IV) hydroxide, and removing the heavy metal precipitate; and adjusting the pH value of the heavy wastewater to 4-6, and then carrying out the salt production step.
8. The method for treating wastewater containing precipitated vanadium according to claim 1, wherein the total chromium content in the wastewater from weight removal is less than or equal to 0.05mg/L and the total vanadium content in the wastewater from weight removal is less than or equal to 0.05mg/L.
9. The method for treating vanadium precipitation wastewater according to claim 2, wherein the refined sodium sulfate at least meets the class III indexes of GB/T6009-2014 industrial anhydrous sodium sulfate; and/or the content of ammonium sulfate in the refined ammonium sulfate is more than 95 percent.
10. A vanadium precipitation wastewater treatment system for implementing the vanadium precipitation wastewater treatment method according to any one of claims 1 to 9, comprising a weight removal system and a salt production system;
the heavy metal removing system is used for removing heavy metal ions in the vanadium precipitation wastewater to obtain heavy metal removing wastewater, and the salt making system is used for treating the heavy metal removing wastewater; the salt making system comprises a primary evaporative crystallization system, a freezing system and a secondary evaporative crystallization system, wherein,
the primary evaporative crystallization system is used for carrying out primary evaporation on the heavy wastewater to obtain primary evaporative crystallization and primary evaporative crystallization mother liquor;
the freezing system is used for freezing the primary evaporative crystallization mother liquor to obtain double salt and freezing mother liquor;
and the secondary evaporation crystallization system is used for carrying out secondary evaporation on the frozen mother liquor to obtain secondary evaporation crystals and secondary evaporation crystal mother liquor.
11. The wastewater treatment system for precipitating vanadium according to claim 10, wherein the salt production system further comprises a first refining system and a second refining system, and the first refining system and the second refining system are respectively used for refining the primary evaporative crystallization and the secondary evaporative crystallization.
12. The wastewater treatment system for precipitating vanadium according to claim 10, wherein the salt production system further comprises a nanofiltration system and a deammoniation system;
the nanofiltration system is used for carrying out nanofiltration on the secondary evaporative crystallization mother liquor for more than one time to obtain nanofiltration concentrated water and nanofiltration produced water;
the deamination system is used for carrying out deamination on the nanofiltration water production to obtain deamination absorption liquid and deamination water production.
13. The wastewater treatment system for precipitating vanadium according to claim 12, wherein the salt production system further comprises a reverse osmosis system, a tertiary evaporative crystallization system and a third refining system;
the reverse osmosis system is used for performing reverse osmosis on the deamination produced water to obtain reverse osmosis concentrated water and reverse osmosis produced water;
the tertiary evaporation crystallization system is used for carrying out tertiary evaporation on the reverse osmosis concentrated water to obtain tertiary evaporation crystals;
and the third refining system is used for refining the tertiary evaporative crystallization to obtain refined sodium chloride.
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